The present invention relates to a poly(benzoic acid), which is a novel compound not known in the prior art nor described in any literatures, a method for the preparation of a poly(benzoic acid) and a method for the preparation of a poly(p-phenylene) having electroconductivity, oxidation-reduction characteristic and excellent heat resistance and suitable as a polymeric electroconductive material and material of a heat-resistant polymer from the poly(benzoic acid).
Poly(p-phenylene) is a known polymeric material having good electroconductivity and excellent heat resistance. Despite these unique properties as an organic polymer, the industrial application field of poly(p-phenylene) is still not so wide because of the difficult problems that poly(p-phenylene) is an insoluble and infusible polymer so that no conventional method is applicable to the molding work of the polymer and that the molecular weight thereof cannot be high enough with a relatively irregular molecular structure not to give a reproducible quality.
A method for the preparation of a poly(p-phenylene) is disclosed in Journal of the American Chemical Society, volume 85, pages 454-458 (1963), according to which benzene is subjected to oxidative polymerization in the presence of aluminum chloride and copper (II) chloride. An alternative method is proposed in Synthetic Metals, volume 44, pages 107-110 (1992), in which benzene is electrolytically polymerized in fuming sulfuric acid to give a poly(p-phenylene). These methods, however, are practically defective since, in the former method, the poly(p-phenylene) is obtained in the form of a powder which is not susceptible to molding and, in the latter method, the polymer obtained has only a quit low degree of polymerization with consequently poor electric and mechanical properties although the polymer is obtained in the form of a film deposited on the surface of the electrode.
Besides, a method is proposed in Macromolecules, volume 21, pages 294-304 (1988), in which a poly(p-phenylene) is obtained in the form of a film through an intermediate having moldability. The polymer obtained by this method, however, does not consist of the 1,4-phenylene units alone but contains about 15% of the 1,2-phenylene units so that the electric properties thereof are not as desired.